1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention is directed at guide wires and their incorporation into diagnostic and therapeutic (multipurpose) catheters.
Currently, diagnostic catheters are steered by a first wire (typically referred to as a moveable guidewire) that is disposed in a lumen running the entire catheter length, typically 90-100 cm. The first wire is longer than the catheter and extends distally from the catheter tip by a variable length, usually from 5-7 cm. The diagnostic catheters are navigated “over the wire” (OTW) to a target vessel, typically a coronary or cerebral artery in an angiography procedure. The purpose of the wire is to steer the catheter as it is advanced through the artery. The wire is advanced first, and the catheter is then advanced over the slides over wire which provides a track for guiding the catheter. This procedure is repeated until the catheter reaches the desired or “target” location, and the wire is then pulled back in the case of an angiography catheter to open the lumen for introducing contrast media.
After the initial angiography or other diagnostic procedure is complete, a balloon or other therapeutic catheter may be “exchanged” for the diagnostic catheter by replacing the first wire with a longer, typically 260-300 cm, exchange wire. The diagnostic catheter is withdrawn over the exchange wire, and the therapeutic catheter then advanced over the exchange wire. The exchange wire must be sufficiently long to allow the physician to be able to grasp some portion of the wire as the diagnostic catheter is withdrawn as well as when the therapeutic catheter is advanced.
Having the entire length of the first wire present in the diagnostic catheter can be disadvantageous in several ways. For example, the wire reduces the flexibility of the catheter making the diagnostic catheter difficult to navigate through tortuous anatomy. Additionally, the space between the inner diameter (ID) of the diagnostic catheter lumen and the outer diameter (OD) of the first wire creates a “shelf”. This shelf can “catch” on the ostium of branch vessels as they take off from the main vessel along the catheter's course.
Currently guidewires used in diagnostic procedures have an outside diameter (OD) from 0.035 inch to 0.038 inch, reducing the flexibility of the diagnostic catheter as it is advanced through the vasculature. One reason for using such larger, stiffer wires is to decrease risk of the “shelving effect” between the catheter and the wire. Using a larger diameter wire reduces the spacing between the catheter lumen's ID and the wire's OD which in turn reduces the height of the shelf and the risk that catheter will engage branch vessels as the catheter is advanced. Such larger diameter wires, however, have the disadvantage that they are less flexible, making navigation of the wires and catheters even more difficult.
A further difficulty with conventional angiography and other diagnostic catheters arises when the first wire is pulled back during advancement of the catheter, Such pull back generates a negative pressure (similar to pull back of a plunger in a syringe) which can release air bubbles from the catheter lumen. The air bubbles can travel distally into the blood stream creating air emboli and potentially causing cause strokes.
Two techniques are commonly used to mitigate air bubbles from migrating distally when the wire is removed: The first technique is known as “double flush” technique in which aspiration with a syringe is performed twice, before establishing anterograde flow; after the second aspiration, the catheter is flushed with heparinized saline and contrast dye. The second technique uses continuous heparinized saline infusion, and when the wire is removed, the rotatory hemostatic valve (RHV) is left open allowing back bleeding; this retrograde bleeding will remove the air bubbles, then the RHV is flushed with saline, and finally anterograde flow is established. Both these techniques add complexity and risk to the procedures.
Most wires have an atraumatic “J” tip, in order to deflect the wire away from vessel walls, and to prevent the wire from dissecting the vessel wall when resistance is found. A less common wire has a straight tip but is malleable, giving the operator the ability to reform the tip, into a desired shape, based on the architecture of the vessel that attempted to be catheterized and to facilitate the a-traumatic catheterization of the vessel. Once the wire “makes a curve”, the catheter is advanced OTW to the desired location.
With current technology the proximal end of the wire is manually rotated by hand with a “pill-roll” finger movement or using a torque device, a collet, that facilitates the necessary grasp to make a clock and counter-clock rotation of the wire. With current diagnostic catheter technology, it is also necessary to pull the wire out prior to the contrast injection which is necessary in order to opacify the target. Both these steps complicate current angiography protocols.
A majority of diagnostic catheters have angled tips, called multipurpose (MP) catheters. A 45° degree MP tip is bent at a 45° degree angle relative to the central axis of the catheter body. The purpose of an angled tip is to allow engaging the origin of larger vessels and then to advances the wire from within. Once the target has been reached, the catheter can slide over the wire. Ideally, MP catheter tips are left along the axis of the target vessel. On the other hand, if a MP catheter is in a straight segment, the angled tip will be against the wall, as shown in FIG. 1, with the potential to cause a dissection to the vessel wall, especially if the wire is advanced forward.
For these reasons, it would be desirable to provide improved guide wire structures and methods for their use in introducing angiography and other vascular diagnostic and therapeutic catheters. It would be particularly desirable to provide diagnostic catheter structures and methods for their use which can eliminate the need to periodically pull back the guide wire as the catheter is advanced, thus simplifying the procedure and lessening the risk of introducing air embolism. It would further be desirable to eliminate any need for more than one lumen in the diagnostic catheter. At least some of these objectives will be met by the inventions described hereinafter.
2. Description of the Background Art
The disclosures described below are relevant background to the present invention:
U.S. Pat. No. 5,114,414 describes a system that includes a multi-lumen catheter. One of those lumens is closed at the distal end, with an “antenna” that comes out the distal closed end. The stated purpose of the wire is to protect the arterial lumen. The other lumens are multipurpose. i.e. to host a wire, instruments, or the like. Having multiple lumens can lead to an undesirable overall increase in the diameter of the catheter.
U.S. Pat. No. 8,764,724 describes a diagnostic or aspiration catheter (FIGS. 7A, 7B and 8) with an obliquely inclined tip having a wire lumen 92 fixed thereto and a guide wire extending therethrough. The patent proposes a multi lumen catheter for coronary application. My invention describes a single lumen catheter. One of the elements of this co-axial system described here includes a beveled catheter on both ends distal and proximal. The proximal segment of the double beveled catheter is attached to a wire that is embedded for the entire length. The wire does not arise from the beveled tip, my invention describes a wire embedded only on the distal tip of a beveled catheter, the one that is presented here comes from a separate element from one of the lumens within the coaxial system. Shows a suction catheter (FIGS. 7A, 8) with an obliquely inclined tip having a wire lumen 92 fixed thereto and a guide wire extending therethrough. The beveled tip increases the cross sectional diameter of the catheter.
U.S. Pat. No. 7,224,250 describes a two lumen aspiration catheter with one lumen having a beveled tip and a second, shorter lumen, providing a rapid exchange system where the wire is not part of the system. There is a shorter catheter that is glued to the distal end of the aspiration catheter; this second lumen allows the passage of a wire. These catheters are advanced to a target location after an initial catheter reaches the target. The initial catheter is then withdrawn and replaced with a second catheter.
U.S. Pat. No. 8,850,960 describes a beveled catheter for arterial puncture like a needle, followed by the insertion of a dilator. The catheter uses a wire that travels within the entire lumen of the catheter but which is not embedded. The purpose is mainly for access and not for navigation aspiration or radiographic contrast injection.
A stent on a wire is described in Sarno et. al. (2010) EuroIntervention 6:413-417. The wire is attached the entire length of the stent, and the device is not intended for primary navigation and requires a separate guiding catheter. The “stent on a wire” does not have a beveled tip.
FIG. 1 shows a prior art MP catheter in a straight section of an artery with a distal tip of the catheter urged against the arterial wall. A magnification in the lower left corner shows deformation of the wall by the catheter tip.